AMD release BIOS that allow you to overclock 7970 from the bios so you don't have to use a program like Trixx or afterburner.
Check the first one out:http://www.legitreviews.com/article/1805/14/
Actually found the bios here:http://forums.guru3d.com/showthread.php?t=359021
I was trying to do it because trixx drives me INSANE. Some times they are clocked some times they aren't it seems like it just randomly shuts itself down some times. I HATE it. Plus i think it would be cool to OC them in the bios so they are always like that even if they change comps, I reformat this that and the other thing.